to put/set the cat among the pigeons – делать или говорить что-то, что внесет раздор, вызовет недовольство
When our company decided not to give any bonuses it put the cat among the pigeons.

to take the bull by the horns – брать быка за рога, действовать решительно
I think you should take the bull by the horns and talk to him.

to back the wrong horse – поставить не на ту лошадь, ошибиться в выборе
The elections proved that white southerners had backed the wrong horse.

to get on one`s high horse – вести себя высокомерно, задаваться
When they started talking about music, David got on his high horse and said that classical music was only fit for museums and archives.

to have a bee in one’s bonnet – быть одержимым какой-то идеей, постоянно говорить о чем-то, иметь идею фикс.
John really has a bee in his bonnet about the environment. He’s always talking about it.

to be a chicken – быть трусом
Don’t be a chicken!

a wolf in sheep’s clothing – волк в овечьей шкуре
Watch out for false prophets. They come to you in sheep’s clothing, but inwardly they are ferocious wolves.

